The proposed work will be directed toward two ends. The first is the improvement of our capability to do genetic manipulations in Dictyostelium discoideum. We will use currently available auxotrophs together with newly developed strains and techniques to make genetic studies more straightforward. Second, we will purify several of the developmentally regulated enzymes involved in chemotaxis in Dictyostelium discoideum. The first of these, cAMP phosphodiesterase is already nearly pure. Once this enzyme has been purified completely, we will use already devised screening methods to isolate structural and regulatory mutants of it. These will be used to study the regulation during the development of cAMP phosphodiesterase and other proteins which are apparently regulated in a similar manner.